FIELD COMPARISON OF CONVENTIONAL AND NEW TECHNOLOGY TEMPERATURE LOGGING SYSTEMS

Field tests were conducted in the summer of 1995 on four state-of-the- art temperature logging systems: an analog, electric-line, system; two pressure and temperature recording memory tools (in-hole computer sys tems); and a Distributed optical fibre Temperature Sensing (DTS) syste m. The tools produced accurate, detailed, temperature versus depth and temperature gradient versus depth logs at depths to 2 km and temperat ures to 200 degrees C. Absolute temperature differences up to 0.4 degr ees C were noted between tools. The computer and electric-line tools h ave significantly better precision and resolution than the DTS, but th e DTS has the advantage of being able to measure temperature instantan eously throughout the hole, and would be well suited for monitoring dy namic systems and gas-filled wells. The multiple independent logs demo nstrate that most of the ''noise'' seen in gradient logs is due to con vection cells, which may have dimensions several times the borehole di ameter, and that these convection cells are currently the limiting fac tor in resolving wellbore temperatures in most settings. (C) 1998 CNR. Published by Elsevier Science Ltd.